The present invention relates to a rolling bearing of the type which is apt to support both radial and axial loads, which bearing will have a high load capacity, as well as very reduced radial dimensions.
In the construction of machines it is often necessary to support in rotation members of various types, particularly shafts, by means of rolling bearings by which the following three conditions have to be complied with at the same time: supporting not only the axial, but also the radial loads acting onto the rotating members, providing a high load capacity, in particular as regards radial loads, and obtaining very limited radial dimensions. These conditions are imposed by the present constructional tendency both towards a more and more complete exploitation of the resistance of the materials and towards the reduction of the dimensions and the increase of the complexity of the mechanical units, particularly in some advanced machine-building fields (aeronautical and automotive).
To support in rotation a rotating member trying to comply with the three mentioned conditions, various types of rolling bearings may be used in combination. According to a first constructional solution, to support the radial loads cylindrical needle bearings may be used (i.e. bearings provided with very thin rings having disposed therebetween one or more rows of cylindrical rollers having a very reduced diameter and a very great length) and to support the axial loads normal thrust bearings, for example ball bearings, may be used. The former are apt to comply with the requirements of high load capacity and reduced radial dimensions, whilst the latter are apt to comply with the axial load capacity requirement. The assemblies obtained in this way are not fully satisfactory, nor are they apt to correspond to the requirements indicated hereinabove. In fact, first of all, they are generally complex and expensive, because of the presence of the two types of bearings which require particular assembly modalities (backing rings, adjustment elements and the like); in addition, if the cylindrical needle bearings correspond to the requirement of limited radial dimensions, this requirement, usually, cannot be completely complied with where normal thrust bearings are used.
A different constructional solution may be obtained by using a pair of taper roller bearings mounted with convergent or divergent taper. If, in this case, the requirement of load capacity in the two main directions (radial and axial) are entirely complied with, the requirement of high load capacity and especially that of limited radial dimensions are not complied with at all. In fact, as is well-known, the radial loads being equal, the taper roller bearings have larger radial dimensions than the cylindrical roller bearings and therefore are able to support heavy loads only when their dimensions are rather large.